Phase changing transformer



,July 21,1931. MURBWAT; 7 1,815,454

PHASE CHANGING TRANSFORMER Filed Jul 10. 192 s 2 Sheets-Sheet 1 (210611754 dlr ala Lat July 21, 1931.

li'g. 4.

M. URBINATI PHASE CHANGING TRANSFORMER Filed July 10, 1928 2 Sheets-Sheet 2 Patented Julyi2l, ll 93 l a a ew-m some Item I -Basie dm me mnensronnnn a 1 Applicatio m g; my 1 tees", fiei ial; No. asmeaa d inltalyl July 25, 1927.

Q r i et-r v tawierme sg not meant o:

ese the tre a e a t e number of he phases, act by varying voltageand the intensity, but theyilgavejgjjaried the nature of the transformed current, in the sense that theatrea form an: al eynatemeeephase a a eae he wr eat ii ewe a terna in mm- Ph e cu rent, iphese entrant i to, ithe wu mat and 9: t; a

I n Wm, owev r-I, that; n sews ca e thetraaeiermer eat only mqdii the 11; te y Qt th i z r ieett M d finne q ien ly it Vol a-get but else transform t e nature t e Wei l: telt a that the sy tem t u nts obtained by the tr nsforrnati n comprises ifiatfiet fr m that at the amber Qt reb t 1 try-an fermekl Sy m-v Gas s at th s ki ,d QJGCLW an area a itc imeta teemere er eially a ee tas. eta t e tra fieifma ea bi elet ric alt rnate cur:

rents atemcontim o isi ai m nt-st emit v ce verse, whi h are the snhfeet matter (I ethe applications of mine en No g'l'l 5 72 of Apr l 2 1 28, and n. p 'a 928 a ute-11191 the tte' storme i SO atta g d hat: besidest e tre ior etl fitmlam tall a leitrenNtive. or meet 919m: sp ntliag to th e tth teed sy tsmi 1 ni he almo he ad iti na el tr mot ve so fa ms, whQfie Phases suitab y di hp e in respect to the phases "of the fundamental tenses. and-at atat at aally,obtala d by th ompetit on at electmmotiv ams; ach o i w h i asf a tiee Of a eleetromotive orces-U a 1 y a It th nt er f t e additiqnal ele t o m r vai e 9 be predated rat n i he r va ues ust. meet det rminate CQQ it QK S, ensid f bl di fic llties are me wi h n sme l transformers in obtaining component electroo the mamma a5 motive forces the valnespf Which are.,eX-

'linentalve t em ti e t r A particnl r method to; overcome this Ciliactly heoir ctiets requir d th? E 1923; e e a a a p l The said'rnethod consists substantially in thaton lya number ofthe turns-of the sec- 50 ondary Winding areiwound upqn he WhQlQ teeny has alreadybeen indicatedin my ear-V lier application Sen. Noly 28 6 953 une 20,

iron of the core, While the remaining turns surround onlya part of the section of the said iron. y 7 I a i Whenthe ratios between thelvaluesofthe component a electromotive forces and the value oi the fundamental electromotive. forceare slmple, and not very numerous, the

above nentioned method answers Well in practice. It becomes, however, practically insuflicient, because it greatly complicates the conetructlon, f the ratios are numerous and the values not simple.

Now, the present invention just for tsobyect to facilitate in suchcases the cone struetion of thetransformer, and the desired result is achieved by the adoption of an ar:

rrangement which simplifiesthe relations be tween the values of the components of the" additional electromotive forces and those of the fundamental electromotive forces, also in theycase inwh-ich the additional e1ectr0-, motive forces are very numerous.

by taking advantage, as Willbe better explained further on, 0f the following consideration In a polyphase system of alterQ natingpurrents all the electromotive forces have the same value; it ensues that if the vectors representing the various phases are arrangedwithl a common origin, they will form a radial; diagram, Where the free ends of \jthe YQC LTQI'S llG on a circle struck with a radiusequal to the common value of the electromotive force of said phases. If it is desired to multiplythe number. of phases, the

Thesiinplification issubsta ntially obtained vectors representing the additional phases \Vl ll I'QSlllt equally spacechbetween the vectors representing ;the primary electromotive forces, and the freeends of said vectors will lie on the same circle above mentioned. Now

tained by the'combination of two component a: circumference equidistant between themselves) have, asarule, relations which are By abandoning the so .ifthe saidadditional phases are to beob neither; rational nor simple in respect of the value of the radius. .nsual conditlon of theexact equivalence of forces and of those of the fundamental electromotive forces, resulting in the above mentioned circular radial diagram, it is stillpossible to form a polyphase system, in which the values of the additional electromotive forces do not materially differ from the value of the fundamental electromotive forcesand this notwithstanding that the additional phases are obtained by the combination of components, the valuesof which are in simple and easily obtainable ratio with the value of the fundamental electromotive' forces retaining their ratio very close to the unity, it is possible to obtain a relation" of the com ponents and of the fundamental forces that assume simple and easily obtainable values; Such a variation of the values of the add1- tional electromotive forces could be made empirically in an arbitrary manner, ascertaining-for each of them the value most approximate to the exact one, which gives values that' are simple in respect to thefrelation be tween the components andthe fundamental electro notive force In pract ce-1t is-possible to proceed in uniform and systematic manner, assuming as values of the additional)electromotive forces the values resulting for them,.-'i iii the diagram of the representative vectors, instead of causing the latter toend'as-is usually the case with their extremities upon a circum- V ference,' (fundamental and additional elec- 'tromotive 'forcesbeing all equal), they be 7 made to endinpoints equally distanced on thecircumference of a regular polygon, at the vertices ofwhichthe vectors of the fundamental currents terminate in the manner.

shown by the figures'of the accompanying drawings, in which Fig.: 1 corresponds to thelcase of theusual polyphase, system in which the electroinotive forces of the fundamental and the additional phases are all equal and the vectors end in equidistant points of a circumference;

Fig. QPcorrespondsto the case of the addi tional electromotive forces the valuesjof which are altered accordingto the invention, so that the representative vectorshave their extremities equall distant on the circumference of a polygon which infthe example given a in the figure is a hexagon;

Fig. 3 refers to thejcase in whichthe poly gQniS a dodecagon, while Fig. 4 shows the arrangement :of the secondary winding in a .three-phase transformer des gned to supply E i-phase transformed current in accordance with this invention. 1

ln'the transformers of the abovementioned type is utilized an arrangement similar to 'tliatappliedfin Pacinottis ring of ordinary jdynames, with the difference that the electromotive forces" acting in the vvarious sectio s of the winding, instead of jbeing prod'u'ced bythe rotation of the ring in an inductive field, areobtained by the static com};

ring vwith a collector of 24 bars, at which terminate the extremities of the successive sections of the"winding,which generate a system of 24 alternate e'lectromotive forces,

phases are displaced betweeneach other These 24 electromotive forces may be repref sented, in the plane, by a'diagrain constituted by 24 vectors having a common point of originin 0, from which they start radially at equalangular intervals of degrees, L

all equal" amongthemselves, but whose 1 ending in 24: points, equidistant among them-.

selves, of a circumference'C, described with the centre in 0 and with a radius equal to the valu V of theelectromotiveiforce between each bar, as shownin Fig. 1. 9

Let us now suppose thatit is required to construct a transformer of alternating currents into continuous currents, or vice 'versa,

capable of producingQ i secondary phases like those above-mentioned, which are ob tained'from a triphase'currentwhich feeds it, the primary windings being arranged on a three colu n core. l t

. From the, secondaryfwindings of thesaid three "columns it is possible to obtaindirectly the, three fundamental electromotive forces together with those opposed to'thein, namely the fo'rces l lig. l, represented the six vectors, 01, 01? 02,02, 03, 03, whose phasesare displaced between each'other' degrees;

In ordertocomplete the desired system of 24 ph ases,:itisnecessary to insert lS other additional phases between the said six fundamental phases, namely three between each two "successive ones, as, l for instance,

t11ose0i,,()5, 06between the two 01, 037, which w" phases are. obtained each by the composition ofoth'er two electromotive forces having convenient value and phase. v

. 1 For the sake iof a betterunderstanding' let us consider the electromotive force represented by vector O5fwhich-finds itself just on'the bisecting line of angle 1103". Its two componentaas; appears in the drawings, are I V the component 05 and the component 5'5 equalamong themselves in value; 9 If, there fore, by V is indicatedthe value of the electromotive force between two bars, namely the vall'ie of the component: 05, which is {also} equal to the radius of circumference G, then In likefmanner, it would be possible to,

1 obtain, for} the components; ofhthe other phases, fractional valuesyexpressed with, many decimal figures, and not reducible, as a rule,exactly to simple fractionscapable of being expressed in slnallnumbers; f

From the foregoing it;willappejar that, inorder to obtainthe exact value ofthe various components, would be necessary to dispose of avery small valueof thevolt/turn, or else to have recourse to asubdivision in numerous parts of the core of the column, to obtain the fractions of volt/turn with the method forming the subject matter of my earlier application ofJune 2Q, 1928, Ser. No. 286,953. r l a a y The1 object of the present "invention is to simplify the construction of the transformer capable of giving the components required for the production 0f the above mentioned additional electromotive 3 forces inserted among the fundamental, ones, and precisely according to this invention, theconstructive simplification is obtained bygreplacing the electromotive forces 01, 04, 05 of Fig; 1, whose terminal points 1, 4, 5 Lare, as has alreadybeen said, distributed at equalin tervalson a circumference C,by other elec tromotivef forces 01, 04, 05, J. whose terminal points 1, 4, are on circumference P of a polygon, which inthe-case shown in Fig. 2 in a hexagon, but might also 'befa 'dodecagon infthe case ofa, couple ofj triphasetrans formers, as will be shownla ter. 1

It is clear that if' points 4, 5, 6 are equallyspacedapart onthe sidesof the polygon, also the corresponding points 4", 5",+6f

L ofthe vector 0l vyillbe at equal distances between each 'Ot herQdiViding the vector itself a into equalparts,- and consequently the 21cm};

pone'nts 04:",05,06f willihav'e values which are simple fractions, expressible in small entire numbers, of thevaluefof the fun'd amental electromotive force VL And as the other components 6"6, 5 5, 4;4 are identical 7 fractions of 03' namely of the same fundamental force v, it wi l be seen that mine component are simple fractions of the fundamental electromoti've forces.

Moreover, it must be observed that ifjthe 'side of the polygon isdivic'led by points'4, 5, ;.into nequal segments,fit will suffice that the winding of the column compris'es'mn kevenl), in order that each 1 component be igivenby an entire number of turns; 1

g'diiference is no ilonger exactly constant but to? the radial polygonal shape, the value of the successive electromotive forces 1 is no longer constant, and alsolrthe angle of; phase the small variationswhich take place are not such'astoiimpair the working of the trans- "former, and theyrare .all the more negligible,

the greater; the number of the sides of the polygon. On theothen hand, it is possible to obtain the very great advantage that the ratio 'between the valuesof the components of the inserted electromotive forcesand the common value V1 ofthe fundamental electromotiveforces becomes very simple. In the if, for. example, the fundamental electromotive force is obtained by awinding of 8 turns,

04 will be obtainedwith turns, 4; With2 turns and so on.

secondary windings in a, three-phase transformer forobtaining the 18 additional phases corresponding male 18 electromotlve forces inserted between the three fundamental ones 01,02,023 andltheir opposites 01', 02', 03, as showninithediagram of Fig. 2. For the sake of clearness, only thosesectionsyof the Secunderstood that the construction is identicalforces ofthe other sectors. i

i w The three cores ofthe transformer, wherely repeated for the. additional electromotive *onarearranged the primary windings pl, 102

and p3gcorresponding to thethree phases of the feeding current supplied by the threephase-line 1, are indicated by 1, 2', 3. In

order to 'obtain the five electromotive forces 0l;04,05,06, 03 of the diagram,Fig. 1, four sectionsof the secondary winding are placed on each of thetwo cores 1,3 and. wound -1I1 opposite directions. The four sections 01,

04, 05Q 06: placed on core 1 compriserespectively 4, 3, 2 and l wholeturns, while the four sections 4'4, 5'5, 6'6, 03 placed on 'core 3 comprise respectively l, 2, 3 ands turns. 1

11 Theiwfree ends ofthe section 01 on core 1 areconnectedbymeans of the wires g, h to the barssa, bof afixedcollector C. The sections 045,05, 06f of core 1 areconnected in series respectively with theoppositelywound sections 44, '55, 6'6 of core 3and theends n 10,? g, g 7' of-each ofsaid pairs of sections a-rerespectively connectedby means of the wires hfl j,jk to the bars I) c, 0 03,61 eof :the same collector C; Finally, the section103, of core8is1connected to the barsef of the collector. Itwillthus be seen th'atthe bars a b,e f correspond respectively to the fundamental electromotive forces 1 01, 03, while i l a thei barsi 6 0,0 03, d e correspond respectively In Fig.4is shownthe arrangement of the tothe additional electromotive forces (id, 05, I

06 obtained by the combination of 04: wit 4x4, 05' with 55,06 ithea,

The stationary collector rests on an insulating ground plate G, and againstthe collector are-mounted the two rotating brushes m and 7 n whichby means of connectlons :not shown phase line 1;

on the. drawings are respectively electrically connected to the revolving rings al 01 upon which rest the collecting'brushes f f which collect the direct current; Thebrushes m and m are driven by'the synchronousmotor M which is also fed A noteworthy simpllcity of construction results from the fact that the fundamental as well as the additionalelectromotive force are obtained by a whole number of turns of the secondary windings, and that thetotal number of turns of the sectionsconnected in series 'to form an additionalelectromotive force is constantland equal to the number of. turns of the sections of the secondary windings supplying the fundamental electromotive forces- "accordancewiththe method forming the subject matter of my earlier application of June 20,1928 Ser. No. 286,953), in the case ofva threecolumn transformer it may be said that if it isdesired to have a secondary winding with number 6a of :phas'es,1namely"with a phases comprisedin each angle of 60 degrees,

it will suffice that the number, representing V,that is the value of one of the fundamental electromotive forces,,be a multiple accord ing to n of the value ofthe volt/turmgthat is to. say that there be thelrelation' V=s n, indicating by s the value'ofthe volt/turn {in otherwords, it will be sufiicient, that the said number he the value of the volt/turn s=V/a,

or a submultiple of this value s=V/'nm.

If,-instead. of one transformer alone, there are available twotransformers, from which it is possible to derive directly 12 fundamental electromotive forces whose'phases are displaced 30 degrees relative toeach other, it'

will be possible to construct for. the fundamental vectors aradial diagram, whereinthe terminal points of; the electromotive forces fall on the circumference of the dodecagon. Fig. 3 represents theficase ofa" secondary V winding. with phases, namely with 5 phases every 30 degrees. 'The 12 fundamental electromotive forces are those 01', O2, 03 corresponding to the verticesof the polygon, and

whose phases are displaced 30 degrees one in respect; to the other; The. arrangement and the connectlon of the sections of. the second ary windings on the cores are the same as in by the currentof the three ofthe smallest of the sections,

Although in theflpreceding explanations has been particularly considered'the-case of; the transformation of a threephasecurrent, it is clear that the same method is applicable 'to polyphase currents of another kind, and al though, for simplicitys sake, has been consideredthe variation of the values of the 1nserted electromotive forces which carry theextremlties of the corresponding vectors from a circumference to the circumference ofQa regular polygon therein described,it is also possible to act in such manner that the values of the additional electromotive forces are individuallyvaried only so slightly as is sufe ficient to reduce their components in such a way as to have simple values with the funda-,

mental electromotive force, alwaysobtaining a good workingiof the transformer. a

It is also understood that, although inthe;

specification and in the drawings only symmetrical arrangements have been considered,

nevertheless the method-allows, to obtain,

when required, asymmetrical arrangements: 3

of the vectors and of the systems ofel'ectro motive forces transformed into whatever number desired, which number may even not electromotive forces.

I claim:

1-. In transformers for polyphase currents of-the type which being fed by a system of alternating currents "comprisingF n/ primary phasestransform it-into asystem of alternating currentscomprising n m phases, the com -be a multiple of that of the fundamental distinct and. separated sections, each section a comprising a whole number of turns chang ing I gradually in the successive sections in sucha manner that all the numbers are of the form k. p,-in which-7r: is an-intcger varying i' froml to m and p the number of the turns *2. Transformers; for" polyphase currents as specified in claim 1, including means for connecting in seriesthe sections of the second;- ary windings of each two cores insuch a manner that the sum of the number of turns'ofl each pair of sections connectedtogether alv waysresults equal tomp, a collector, and

means for connecting the bars of the collector V with said pairs; of sections and with the sec tions, one on eachcore, the number of turns of which is also mp, the arrangement being. such that by tapping the currents delivered at 'the bars of the collector, a system 'of electromotive forces is obtained so interrelated that the diagram of the corresponding vectorsis a radialone with the ends of the vectors distributed at equal distances, on the sides ofa regular polygon. 3. Intransformers for polyphase currents 6 :the "caseofr the transformer shown in Fig. 4. ofthe type which being fed by a systemofalternating currents comprising n primary phases transform it into a system of alternating currents comprising Qnm phases,the combination of n cores,n primary windings,

15 one for eachof said cores, through which circulate the n alternating currents of the feeding system, 42 secondary windings each comprising 2m distinct and separated sections, mof the said sections being wound in the opposite direction of the other m, each section comprising a Wholenumber of turns, changing gradually in the successive sections of each set wound in the samedirection in such a manner that all the numbersareofthe form is p, inwhich la isan integer Varying i from Z to m and p the number ofturns of the smallest of the sections. a t

4. Transformer for polyphase currents as specified in claim '3 including means for connecting in series the oppositely wound sections of the secondary windings of each two cores in such a manner that the sum of the number of turns of eachpair of sections connected togetheralways result equal to mp, a collector, and meansfor connecting the bars of the collectorwith the said pairsof sections and with the sections,two oppositely wound on each core, the number of turns of which I is also mp, the arrangement fbeinggsuchthat by tapping the currents delivered at the bar of the collector, a system of electromotive forces is obtained so interrelated that the diagram of the corresponding vectors is a radial one with the ends of the Vectors distributed at equal distances on] the sidesofa regular polygon. l i a In testimony whereof I haveafiixed my signature at Rome, Italy,tliis26th day of June,1928. i t

MARIO URBINATI. 

